from functools import reduce
DIGITS = {'0': 0, '1': 1, '2': 2, '3': 3, '4': 4, '5': 5, '6': 6, '7': 7, '8': 8, '9': 9}
def str2int(s):
    def fn(x,y):
        return x * 10 + y
    def char2num(s):
        return DIGITS[s]
    #return reduce(fn,map(char2num,s))
    #lambda函数
    return reduce(lambda x,y:x* 10 + y,map(char2num,s))
res = str2int('1357')
print('res = ',res)

